The ciliate protozoan Paramecium tetraurelia was previously shown to contain a heme-pigment which had similar spectroscopic properties to mammalian myoglobins and hemoglobins. Subsequent studies in our laboratory showed the heme protein to exist in five electrophoretic forms with isoelectric points of 5.54, 5.18, 4.98, 4.51 and 4.16 respectively. Analysis of partially purified mixtures of the myoglobin isozymes from paramecium by SDS gel electrophoresis suggested a single molecular weight species of approximately 16,000 daltons. The present project is concerned with the purification of all five myoglogin forms in pure form and their physical and chemical characterization by various techniques.